Honestly, it's a hard choice in dealing with enemies in levels that weren't really designed for them. I personally think using enemies where appropriate improves our game as it provides some extra complexity by forcing players to deal with more things at once. The problem is that a lot of our stages, such as ERZ, weren't really designed with enemies in mind, making their use really complicated. Optimally the enemies would be part of the design from the start, but in ERZ's case the enemies were created later for the most part.

Hence, how those snailers got in there as we retrofitted the map to have enemies. Some of them more successful than others =P

Well to be honest, you could just make some slight modifications to the snailers themselves. A wider projectile and a telegraph before firing would give it both better visibility and make it easier to anticipate.